How do light materials work in OB baffles?
Many of you recommend using light, somewhat flexible material for test baffles for OB. How does this work? As I understand things, the pressure waves on the front and rear of the baffles are exactly out of phase, thus trying to push the baffles one way or another. If the OB baffle is made of anything other than very rigid material, it will begin to flex almost as an extension of the cone itself. Therefore, any audition you do with such a baffle will give you results very different from baffles made of rigid material. Can you please explain how the physics is supposed to work with light and flexible OB baffles?johninCR said:
You're right but it doesn't move that much, I guess because the mass of the driver is so much more than the cone and the air it is moving (sorry just the cone and vc, since the air has a void on the opposite side). If you hold a driver in your hands and play it, it doesn't try to jump out of your hands, does it? Also, cardboard isn't very resonant so for testing it may be better than say very thin plywood. For heavier drivers I just put some wood or something under the magnet for support and they don't seem to move at all. The baffles get very little stress on them compared to any other type of enclosure.
The test baffle first would show you what OB is like and you can hear what different shapes and sizes sound like before building. What other enclosure can you do that with? If you use big swept back wings you can get resonances that cardboard may not reveal. One way to avoid that is making them adjustable with hinges, leather, etc. Bracing helps unless it's a cavity resonance which happened on my first attempt. It was a huge peak at 110hz, but I had equal size but tapered wings. All I did was cut 2" off one of the wings and it went away. Now I always make them different sizes even though they are tapered.
I don't think cardboard or anything else flimsy would work for testing a W baffle sub, but you can use it make sure the driver is going to give you bass on OB. I use alot of cheap drivers that don't have specs, so I just evaluate them by listening. The only other spec you need is the Fs and that's easy enough.
The test baffle first would show you what OB is like and you can hear what different shapes and sizes sound like before building. What other enclosure can you do that with? If you use big swept back wings you can get resonances that cardboard may not reveal. One way to avoid that is making them adjustable with hinges, leather, etc. Bracing helps unless it's a cavity resonance which happened on my first attempt. It was a huge peak at 110hz, but I had equal size but tapered wings. All I did was cut 2" off one of the wings and it went away. Now I always make them different sizes even though they are tapered.
I don't think cardboard or anything else flimsy would work for testing a W baffle sub, but you can use it make sure the driver is going to give you bass on OB. I use alot of cheap drivers that don't have specs, so I just evaluate them by listening. The only other spec you need is the Fs and that's easy enough.
tom1356 said:
That's exactly what I'm using with my Ravens (both systems). If you want to keep the same crossover point, you won't be able to effectively use MTM.
I also had MTM setup (with Triangle mids) and tried 12K crossover and it sounded very bad. Highs were cancelling and overall sound was so bad that I wasn't using that system at all for almost a year.
For MTM you need a low crossover point, 3kHz or so, but you can't use first order filter, but at least 3rd order and then the magic is gone, if you know what I mean. Even Shaktis won't help
So finally, taking advice from Thorsten, I used low pass filter on one of the mids (around 1K, I think) and I'm using the other one full range with ribbon filling in, above 12k. It changed the whole system tremendously and the sound is very good now. It's basicaly TM with another midrange filling mdbass.
If I built another speaker, I wouldn't go with MTM. TM seem to sound much better.
Konnichiwa,
Are you sure? One of the spreadsheets a forum search should have revealed is this one:
http://www.exdreamnet.de/download/Xlbaffle.xls
Sayonara
GeorgeBoles said:
Are you sure? One of the spreadsheets a forum search should have revealed is this one:
http://www.exdreamnet.de/download/Xlbaffle.xls
Sayonara
Just a question: Is it a good idea to use a single dipole sub help my OB´s in the low range?
It seems like people always use stereo subs, is there a particular reason for that?
I have four nice 12" woofers in my old H-type subs, but two of them are glued (!) into the boxes and getting them out if there would be a nightmare. The other two would be nice in a W baffle, though.
Would there be any benefits (or drawbacks) in feeding each woofer in a W baffle from the two stereo channels instead of a mixed mono signal?
It seems like people always use stereo subs, is there a particular reason for that?
I have four nice 12" woofers in my old H-type subs, but two of them are glued (!) into the boxes and getting them out if there would be a nightmare. The other two would be nice in a W baffle, though.
Would there be any benefits (or drawbacks) in feeding each woofer in a W baffle from the two stereo channels instead of a mixed mono signal?
I have always believed two subs to be better than one.
However, while I save up for a pair of dipole subs, I have put together a single coupled-cavity sub and have to say that it is not bad at all.
I would guess one dipole sub would probably work even better, providing it doesn't have to go higher than about 100 Hz (mine is working up to 70 Hz)
I would guess in a W baffle, it is best to feed both woofers with a combined signal. Are you absolutely sure that you cannot rescue those other two drivers?
And do those drivers have a high Qts and reasonable X-max parameters for dipole use?
However, while I save up for a pair of dipole subs, I have put together a single coupled-cavity sub and have to say that it is not bad at all.
I would guess one dipole sub would probably work even better, providing it doesn't have to go higher than about 100 Hz (mine is working up to 70 Hz)
I would guess in a W baffle, it is best to feed both woofers with a combined signal. Are you absolutely sure that you cannot rescue those other two drivers?
And do those drivers have a high Qts and reasonable X-max parameters for dipole use?
I too believe that two subs are better than one, but I´m running out of space here
The crossover frequency will probably be 50-60Hz or something.
Those two glued drivers *can* be rescued, but it would be less trouble to buy a new pair
These are dirt cheap woofers (Pro Audio SW12), but some people here in Sweden have used them in dipole subs with success.
The problem is, as I mentioned, space.
Another alternative could be a single XLS 10" in a regular box, possibly with a passive driver or two. A friend has a pair in his floor standing speakers and I´m truly impressed by their floor-shaking capabilities
BTW I just had an idea minutes ago: We have H baffles and W baffles, what about N baffles? Imagine half a W baffle with only one driver.
Good or bad idea?
The crossover frequency will probably be 50-60Hz or something.
Those two glued drivers *can* be rescued, but it would be less trouble to buy a new pair
These are dirt cheap woofers (Pro Audio SW12), but some people here in Sweden have used them in dipole subs with success.
The problem is, as I mentioned, space.
Another alternative could be a single XLS 10" in a regular box, possibly with a passive driver or two. A friend has a pair in his floor standing speakers and I´m truly impressed by their floor-shaking capabilities
BTW I just had an idea minutes ago: We have H baffles and W baffles, what about N baffles? Imagine half a W baffle with only one driver.
Good or bad idea?
Peter Daniel said:
That's exactly what I'm using with my Ravens (both systems). If you want to keep the same crossover point, you won't be able to effectively use MTM.
I also had MTM setup (with Triangle mids) and tried 12K crossover and it sounded very bad. Highs were cancelling and overall sound was so bad that I wasn't using that system at all for almost a year.
For MTM you need a low crossover point, 3kHz or so, but you can't use first order filter, but at least 3rd order and then the magic is gone, if you know what I mean. Even Shaktis won't help
So finally, taking advice from Thorsten, I used low pass filter on one of the mids (around 1K, I think) and I'm using the other one full range with ribbon filling in, above 12k. It changed the whole system tremendously and the sound is very good now. It's basicaly TM with another midrange filling mdbass.
If I built another speaker, I wouldn't go with MTM. TM seem to sound much better.
I think I will stick with the single mid run full range with the 12k first order on the tweeter.
I will be experimenting with two woofers in the W baffle plus another of the same type woofer on the main open baffle with the mid and tweet.
I think I might build some gainclones for the subs and run the mid tweet and woofer baffle from the 300b amps.
Any other ideas or suggestions?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.